BFWillie,
I meant that this survey seemed a little better than many of the surveys on BFR that have been mentioned in these forums (when researchers are seeking to recruit participants). So I was speaking in relative, not absolute, terms. The University of Delaware study strikes me as the strongest to date, with its main limitation (based on what I know about it from participating in it) being that it doesn't have a comparison group of shod runners. If they do, then that'd make their work significantly stronger.
Many months ago in this forum I disagreed with a researcher who was trying to recruit participants for his study because he was using a nonsensical definition of injury. The current survey doesn't suffer from this problem. And it doesn't suffer from a number of problems that other surveys promoted in these forums have had, such as inability to distinguish from barefoot vs. minimalist running and lack of information on injury history prior to running barefoot/minimalist, among other flaws.
I haven't tried to respond twice to this survey, but most survey services, like Survey Monkey, enable the researcher to prevent multiple responses from the same computer (as indicated by IP address). Even when that's in place, it can't deter a motivated person from responding multiple times as he or she could just use another computer. So I agree with you that in this kind of situation where there are passionate partisans on different sides, there is the potential for the results to be biased.